Photoelectric conversion element and solid-state imaging device

ABSTRACT

A photoelectric conversion element according to an embodiment of the present disclosure includes: a first electrode  15   a  and a second electrode  18  facing each other; and a photoelectric conversion layer  17  provided between the first electrode  15   a  and the second electrode  18 , and including a first quinacridone derivative represented by a formula (1).

CROSS REFERENCE TO RELATED APPLICATIONS

This application a continuation of U.S. patent application Ser. No.15/770,976 filed Apr. 25, 2018 which is a national stage applicationunder 35 U.S.C. 371 and claims the benefit of PCT Application No.PCT/JP2016/078208 having an international filing date of 26 Sep. 2016,which designated the United States, which PCT application claimed thebenefit of Japanese Priority Patent Application 2015-215966 filed on 2Nov. 2015, the disclosures of each of which are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to, for example, a photoelectricconversion element using an organic semiconductor and a solid-stateimaging device including the same.

BACKGROUND ART

In recent years, in solid-state imaging devices such as CCD (ChargeCoupled Device) image sensors or CMOS (Complementary Metal OxideSemiconductor) image sensors, reduction in pixel size has accelerated.This reduces the number of photons entering a unit pixel, which resultsin reduction in sensitivity and reduction in S/N ratio. Moreover, in acase where a color filter including a two-dimensional array ofprimary-color filters of red, green, and blue is used for colorization,in a red pixel, green light and blue light are absorbed by the colorfilter, which causes reduction in sensitivity. Further, in order togenerate each color signal, interpolation between pixels is performed,which causes so-called false color.

Accordingly, for example, PTL 1 discloses an image sensor using anorganic photoelectric conversion film having a multilayer configurationin which an organic photoelectric conversion film having sensitivity toblue light (B), an organic photoelectric conversion film havingsensitivity to green light (G), and an organic photoelectric conversionfilm having sensitivity to red light (R) are stacked in order. In thisimage sensor, signals of B, G, and R are separately extracted from onepixel to achieve an improvement in sensitivity. PTL 2 discloses animaging element in which an organic photoelectric conversion filmincluding a single layer is formed, a signal of one color is extractedfrom the organic photoelectric conversion film, and signals of twocolors are extracted by silicon (Si) bulk spectroscopy. In so-calledstacked imaging elements (image sensors) disclosed in PTLs 1 and 2, mostof incident light is subjected to photoelectric conversion and is read,which results in visible light use efficiency of nearly 100%. Moreover,each light receiver obtains color signals of three colors R, G, and B,which makes it possible to generate an image having high sensitivity andhigh resolution (invisible false color).

Accordingly, for example, PTL 3 disclosures a solid-state imagingelement including a photoelectric conversion film that containsquinacridone or a derivative thereof in order to achieve a furtherimprovement in sensitivity, that is, improvements in external quantumefficiency (EQE) and a spectroscopic shape. Moreover, NPL 1 reports animage sensor having responsivity improved by a photoelectric conversionlayer containing dimethylquinacridone and subphthalocyanines.

CITATION LIST Patent Literature

-   PTL 1: Japanese Unexamined Patent Application Publication No.    2003-234460-   PTL 2: Japanese Unexamined Patent Application Publication No.    2005-303266-   PTL 3: Japanese Unexamined Patent Application Publication No.    2007-234651

Non-Patent Literature

-   NPL 1: J. Phys. Chem.C 2014,118,13424-13431

SUMMARY OF THE INVENTION

However, in a case where one or two characteristics of the spectroscopicshape, responsivity, and EQE are improved, there is an issue that theother characteristics are deteriorated.

It is therefore desirable to provide a photoelectric conversion elementand a solid-state imaging device that allow for achievement of asuperior spectroscopic shape, high responsivity, and high externalquantum efficiency.

A photoelectric conversion element according to an embodiment of thepresent disclosure includes: a first electrode and a second electrodefacing each other; and a photoelectric conversion layer provided betweenthe first electrode and the second electrode, and including a firstquinacridone derivative represented by the following formula (1).

(where each of R1 and R2 is independently one of an alkyl group, analkenyl group, an alkynyl group, an aryl group, a cyano group, a nitrogroup, and a silyl group, each of m1 and m2 is independently 0 or aninteger of 1 or more, in a case where each of m1 and m2 is 2 or more,two or more R1 are optionally bound to one another to form a ring andtwo or more R2 are optionally bound to one another to form a ring, andR3 is one of an alkyl group, an aryl group, and a heterocyclic group.)

A solid-state imaging device according to an embodiment of the presentdisclosure includes pixels each including one or more organicphotoelectric converters, and includes the photoelectric conversionelement according to the foregoing embodiment of the present disclosureas each of the organic photoelectric converters.

In the photoelectric conversion element according to the embodiment ofthe present disclosure and the solid-state imaging device according tothe embodiment of the present disclosure, the photoelectric conversionlayer between the first electrode and the second electrode facing eachother is formed using the first quinacridone derivative represented bythe foregoing formula (1), which improves carrier (hole and electron)transport performance and carrier use efficiency in the photoelectricconversion layer.

According to the photoelectric conversion element of the embodiment ofthe present disclosure and the solid-state imaging device of theembodiment of the present disclosure, the photoelectric conversion layeris formed using the first quinacridone derivative represented by theforegoing formula (1), which improves carrier transport performance anduse efficiency in the photoelectric conversion layer. This makes itpossible to improve responsivity and external quantum efficiency whilemaintaining a sharp spectroscopic shape. In other words, it is possibleto provide a photoelectric conversion element achieving a superiorspectroscopic shape, high responsivity, and high EQE, and a solid-stateimaging device including the photoelectric conversion element. It is tobe noted that effects described herein are not necessarily limited, andany of effects described in the present disclosure may be included.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a schematic configuration of aphotoelectric conversion element according to a first embodiment of thepresent disclosure.

FIG. 2 is a plan view of a relationship among forming positions of anorganic photoelectric conversion layer, a protective layer (an upperelectrode), and a contact hole.

FIG. 3A is a cross-sectional view of a configuration example of aninorganic photoelectric converter.

FIG. 3B is another cross-sectional view of the inorganic photoelectricconverter illustrated in FIG. 3A.

FIG. 4 is a cross-sectional view of a configuration (lower-side electronextraction) of an electric charge (electron) storage layer of an organicphotoelectric converter.

FIG. 5A is a cross-sectional view for description of a method ofmanufacturing the photoelectric conversion element illustrated in FIG. 1.

FIG. 5B is a cross-sectional view of a process subsequent to the processin FIG. 5A.

FIG. 6A is a cross-sectional view of a process subsequent to the processin FIG. 5B.

FIG. 6B is a cross-sectional view of a process subsequent to the processin FIG. 6A.

FIG. 7A is a cross-sectional view of a process subsequent to the processin FIG. 6B.

FIG. 7B is a cross-sectional view of a process subsequent to the processin FIG. 7A.

FIG. 7C is a cross-sectional view of a process subsequent to the processin FIG. 7B.

FIG. 8 is a main-part cross-sectional view that describes workings ofthe photoelectric conversion element illustrated in FIG. 1 .

FIG. 9 is a schematic view for description of workings of thephotoelectric conversion element illustrated in FIG. 1 .

FIG. 10 is a cross-sectional view of a schematic configuration of aphotoelectric conversion element according to a second embodiment of thepresent disclosure.

FIG. 11 is a functional block diagram of a solid-state imaging deviceusing the photoelectric conversion element illustrated in FIG. 1 as apixel.

FIG. 12 is a block diagram illustrating a schematic configuration of anelectronic apparatus using the solid-state imaging device illustrated inFIG. 11 .

MODES FOR CARRYING OUT THE INVENTION

In the following, some embodiments of the present disclosure aredescribed in detail with reference to the drawings. It is to be notedthat description is given in the following order.

1. First Embodiment (An example in which an organic photoelectricconversion layer is formed using an HR-type quinacridone derivative)

1-1. Configuration of Photoelectric Conversion Element

1-2. Method of Manufacturing Photoelectric Conversion Element

1-3. Workings and Effects

2. Second Embodiment (An example in which an organic photoelectricconversion layer is formed using two kinds of quinacridone derivatives,i.e., HR-type and HH-type quinacridone derivatives)

3. Application Examples 4. Examples 1. First Embodiment

FIG. 1 illustrates a cross-sectional configuration of a photoelectricconversion element (a photoelectric conversion element 10) according toa first embodiment of the present disclosure. The photoelectricconversion element 10 configures, for example, one pixel of asolid-state imaging device (to be described later) such as a CCD imagesensor and a CMOS image sensor. In the photoelectric conversion element10, a pixel transistor (including transfer transistors Tr1 to Tr3 to bedescribed later) is formed and a multilayer wiring layer (a multilayerwiring layer 51) is included on a front surface (a surface S2 oppositeto a light reception surface) of a semiconductor substrate 11.

The photoelectric conversion element 10 according to the presentembodiment has a configuration in which one organic photoelectricconverter 11G and two inorganic photoelectric converters 11B and 11R arestacked along a vertical direction. Each of the organic photoelectricconverter 11G and the inorganic photoelectric converters 11B and 11Rselectively detects light in a relevant one of wavelength regionsdifferent from one another, and performs photoelectric conversion on thethus-detected light. The organic photoelectric converter 11G is formedusing a quinacridone derivative (a first quinacridone derivative)represented by a formula (1) to be described later.

(1-1. Configuration of Photoelectric Conversion Element)

The photoelectric conversion element 10 has a stacked configurationincluding one organic photoelectric converter 11G and two inorganicphotoelectric converters 11B and 11R, which allows one element to obtainrespective color signals of red (R), green (G), and blue (B). Theorganic photoelectric converter 11G is formed on a back surface (asurface S1) of the semiconductor substrate 11, and the inorganicphotoelectric converters 11B and 11R are formed to be embedded in thesemiconductor substrate 11. Hereinafter, description is given ofconfigurations of respective components.

(Organic Photoelectric Converter 11G)

The organic photoelectric converter 11G is an organic photoelectricconversion element that absorbs light in a selective wavelength region(green light herein) with use of an organic semiconductor to generateelectron-hole pairs. The organic photoelectric converter 11G has aconfiguration in which an organic photoelectric conversion layer 17 issandwiched between a pair of electrodes (a lower electrode 15 a and anupper electrode 18) for extraction of signal electric charges. The lowerelectrode 15 a and the upper electrode 18 are electrically coupled toconductive plugs 120 a 1 and 120 b 1 embedded in the semiconductorsubstrate 11 through a wiring layer and a contact metal layer, asdescribed later. It is to be noted that the organic photoelectricconversion layer 17 corresponds to a specific example of an “organicsemiconductor layer” in the present disclosure.

Specifically, in the organic photoelectric converter 11G, interlayerinsulating films 12 and 14 are formed on the surface S1 of thesemiconductor substrate 11, and the interlayer insulating film 12 isprovided with through holes in regions facing the respective conductiveplugs 120 a 1 and 120 b 1 to be described later. Each of the throughholes is filled with a relevant one of conductive plugs 120 a 2 and 120b 2. In the interlayer insulating film 14, wiring layers 13 a and 13 bare respectively embedded in regions facing the conductive plugs 120 a 2and 120 b 2. The lower electrode 15 a and the wiring layer 15 b areprovided on the interlayer insulating film 14. The wiring layer 15 b iselectrically isolated by the lower electrode 15 a and an insulating film16. The organic photoelectric conversion layer 17 is formed on the lowerelectrode 15 a out of them, and the upper electrode 18 is so formed asto cover the organic photoelectric conversion layer 17. As described indetail later, a protective layer 19 is so formed on the upper electrode18 as to cover a surface of the upper electrode 18. The protective layer19 is provided with a contact hole H in a predetermined region, and acontact metal layer 20 is so formed on the protective layer 19 as to becontained in the contact hole H and to extend to a top surface of thewiring layer 15 b.

The conductive plug 120 a 2 serves as a connector together with theconductive plug 120 a 1, and forms, together with the conductive plug120 a 1 and the wiring layer 13 a, a transmission path of electriccharges (electrons) from the lower electrode 15 a to a green electricstorage layer 110G to be described later. The conductive plug 120 b 2serves as a connector together with the conductive plug 120 b 1, and theconductive plug 120 b 2 forms, together with the conductive plug 120 b1, the wiring layer 13 b, the wiring layer 15 b, and the contact metallayer 20, a discharge path of electric charges (holes) from the upperelectrode 18. In order to allow each of the conductive plugs 120 a 2 and120 b 2 to also serve as a light-blocking film, each of the conductiveplugs 120 a 2 and 120 b 2 desirably includes, for example, a laminatedfilm including metal materials such as titanium (Ti), titanium nitride(TiN), and tungsten. Moreover, such a laminated film is desirably used,which makes it possible to secure contact with silicon even in a casewhere each of the conductive plugs 120 a 1 and 120 b 1 is formed as ann-type or p-type semiconductor layer.

The interlayer insulating film 12 desirably includes an insulating filmhaving a small interface state in order to reduce an interface statewith the semiconductor substrate 11 (a silicon layer 110) and tosuppress generation of a dark current from an interface with the siliconlayer 110. As such an insulating film, it is possible to use, forexample, a laminated film including a hafnium oxide (HfO₂) film and asilicon oxide (SiO₂) film. The interlayer insulating film 14 includes asingle-layer film including one of materials such as silicon oxide,silicon nitride, and silicon oxynitride (SiON), or includes a laminatedfilm including two or more of these materials.

The insulating film 16 includes, for example, a single-layer filmincluding one of materials such as silicon oxide, silicon nitride, andsilicon oxynitride (SiON) or a laminated film including two or more ofthese materials. The insulating film 16 has, for example, a planarizedsurface, thereby having a shape and a pattern that each have almost nodifference in level between the insulating film 16 and the lowerelectrode 15 a. In a case where the photoelectric conversion element 10is used as each of pixels of the solid-state imaging device, theinsulating film 16 has a function of electrically isolating the lowerelectrodes 15 a of the respective pixels from one another.

The lower electrode 15 a is provided in a region that faces lightreception surfaces of the inorganic photoelectric converters 11B and 11Rformed in the semiconductor substrate 11 and covers these lightreception surfaces. The lower electrode 15 a includes a conductive filmhaving light transparency, and includes, for example, ITO (indium tinoxide). Alternatively, as a constituent material of the lower electrode15 a, other than ITO, a tin oxide (SnO₂)-based material doped with adopant or a zinc oxide-based material prepared by doping aluminum zincoxide (ZnO) with a dopant may be used. Examples of the zinc oxide-basedmaterial include aluminum zinc oxide (AZO) doped with aluminum (Al) as adopant, gallium zinc oxide (GZO) doped with gallium (Ga), and indiumzinc oxide (IZO) doped with indium (In). Moreover, other than thesematerials, for example, CuI, InSbO₄, ZnMgO, CuInO₂, MgIN₂O₄, CdO,ZnSnO₃, etc. may be used. It is to be noted that in the presentembodiment, signal electric charges (electrons) are extracted from thelower electrode 15 a; therefore, in the solid-state imaging device to bedescribed later that uses the photoelectric conversion element 10 aseach of the pixels, the lower electrode 15 a is formed separately foreach of the pixels.

The organic photoelectric conversion layer 17 includes one or both of anorganic p-type semiconductor and an organic n-type semiconductor.Moreover, the organic photoelectric conversion layer 17 performsphotoelectric conversion on light in a selective wavelength region, andallows light in other wavelength regions to pass therethrough. Herein,the organic photoelectric conversion layer 17 has, for example, amaximal absorption wavelength in a range from 450 nm to 650 nm bothinclusive.

In the present embedment, the organic photoelectric conversion layer 17preferably uses a quinacridone derivative represented by the followingformula (1), that is, a so-called HR-type quinacridone derivative inwhich one of two amine sites in a molecule is secondary amine (NHRR′)and the other is tertiary amine (NRR′R″), because the HR-typequinacridone derivative has relatively small crystal grains (grains) tobe formed in a film. Accordingly, carriers (holes and electrons)efficiently move in an interface between the crystal grains (a crystalgrain boundary). Moreover, a carrier trap derived from a gap between thegrains is reduced.

(where each of R1 and R2 is independently one of an alkyl group, analkenyl group, an alkynyl group, an aryl group, a cyano group, a nitrogroup, and a silyl group, each of m1 and m2 is independently 0 or aninteger of 1 or more, in a case where each of m1 and m2 is 2 or more,two or more R1 are optionally bound to one another to form a ring andtwo or more R2 are optionally bound to one another to form a ring, andR3 is one of an alkyl group, an aryl group, and a heterocyclic group.)

Specific examples of the quinacridone derivative represented by theforegoing formula (1) include compounds represented by the followingformulas (1-1) to (1-16), etc.

Moreover, the organic photoelectric conversion layer 17 preferablyincludes a subphthalocyanine derivative represented by the followingformula (2) together with the foregoing HR-type quinacridone derivative.

(where each of R4 to R15 is independently a hydrogen atom, a halogenatom, a straight-chain, branched, or cyclic alkyl group, a thioalkylgroup, a thioaryl group, an arylsulfonyl group, an alkylsulfonyl group,an amino group, an alkylamino group, an arylamino group, a hydroxygroup, an alkoxy group, an acylamino group, an acyloxy group, a phenylgroup, a carboxy group, a carboxyamide group, a carboalkoxy group, anacyl group, a sulfonyl group, a cyano group, and a nitro group, anyadjacent ones of R4 to R15 are optionally bound to one another to form aring, and X is an anionic group.)

Specific examples of the subphthalocyanine derivative represented by theformula (2) include compounds represented by the following formulas(2-1) to (2-4), etc.

It is to be noted that in the present embodiment, the foregoing HR-typequinacridone derivative serves as an organic p-type semiconductor, andthe foregoing subphthalocyanine derivative serves as an organic n-typesemiconductor.

The organic photoelectric conversion layer 17 preferably includes theHR-type quinacridone derivative represented by the foregoing formula (1)within, for example, a range from 25% to 75% both inclusive in volumeratio. A content of the HR-type quinacridone derivative is within theforegoing range, which reduces a bias in probabilities that p-typeHR-type quinacridone derivatives are adjacent each other, the n-typesubphthalocyanine derivatives are adjacent each other, and the p-typeHR-type quinacridone derivative and the n-type subphthalocyaninederivative are adjacent to each other in the organic photoelectricconversion layer 17. Accordingly, a possibility that an exciton reachesan interface between the p-type HR-type quinacridone derivative and then-type subphthalocyanine derivative is ensured. Moreover, transportefficiency of holes passing through between the adjacent p-type HR-typequinacridone derivatives and transport efficiency of electrons passingthrough between the adjacent n-type subphthalocyanine derivatives afterexciton dissociation are ensured. This makes high external quantumefficiency and high responsivity compatible.

Any other unillustrated layer may be provided between the organicphotoelectric conversion layer 17 and the lower electrodes 15 a andbetween the organic photoelectric conversion layer 17 and the upperelectrode 18. For example, an undercoat film, a hole transport layer, anelectron blocking film, the organic photoelectric conversion layer 17, ahole blocking film, a buffer film, an electron transport layer, and awork function adjustment film may be stacked in order from the lowerelectrode 15 a.

The upper electrode 18 includes a conductive film having lighttransparency, as with the lower electrode 15 a. In the solid-stateimaging device using the photoelectric conversion element 10 as each ofthe pixels, the upper electrode 18 may be separately provided for eachof the pixels, or may be formed as a common electrode for the respectivepixels. The upper electrode 18 has, for example, a thickness of 10 nm to200 nm both inclusive.

The protective layer 19 includes a material having light transparency,and is, for example, a single-layer film including one of materials suchas silicon oxide, silicon nitride, and silicon oxynitride or a laminatedfilm including two or more of these materials. The protective layer 19has, for example, a thickness of 100 nm to 30000 nm both inclusive.

The contact metal layer 20 includes, for example, one of materials suchas titanium, tungsten, titanium nitride, and aluminum, or includes alaminated film including two or more of these materials.

The upper electrode 18 and the protective layer 19 are so provided as tocover the organic photoelectric conversion layer 17, for example. FIG. 2illustrates planar configurations of the organic photoelectricconversion layer 17, the protective layer 19 (the upper electrode 18),and the contact hole H.

Specifically, an edge e2 of the protective layer 19 (the upper electrode18 is similar to the protective layer 19) is located outside of an edgee1 of the organic photoelectric conversion layer 17, and the protectivelayer 19 and the upper electrode 18 are so formed as to protrude towardoutside of the organic photoelectric conversion layer 17. Morespecifically, the upper electrode 18 is so formed as to cover a topsurface and a side surface of the organic photoelectric conversion layer17, and as to extend onto the insulating film 16. The protective layer19 is so formed as to cover a top surface of such an upper electrode 18,and is formed in a similar planar shape to that of the upper electrode18. The contact hole H is provided in a region not facing the organicphotoelectric conversion layer 17 (a region outside of the edge e1) ofthe protective layer 19, and allows a portion of a surface of the upperelectrode 18 to be exposed from the contact hole H. A distance betweenthe edges e1 and e2 is not particularly limited, but is, for example,within a range from 1 μm to 500 μm both inclusive. It is to be notedthat in FIG. 2 , one rectangular contact hole H along an end side of theorganic photoelectric conversion layer 17 is provided; however, a shapeof the contact hole H and the number of the contact holes H are notlimited thereto, and the contact hole H may have any other shape (forexample, a circular shape, a square shape, etc.), and a plurality ofcontact holes H may be provided.

The planarization layer 21 is so formed on the protective layer 19 andthe contact metal layer 20 as to cover entire surfaces of the protectivelayer 19 and the contact metal layer 20. An on-chip lens 22 (amicrolens) is provided on the planarization layer 21. The on-chip lens22 concentrates light incoming from a top of the on-chip lens 22 ontoeach of light reception surfaces of the organic photoelectric converter11G and the inorganic photoelectric converters 11B and 11R. In thepresent embodiment, the multilayer wiring layer 51 is formed on thesurface S2 of the semiconductor substrate 11, which makes it possible todispose the respective light reception surfaces of the organicphotoelectric converter 11G and the inorganic photoelectric converters11B and 11R close to one another, and to reduce variation in sensitivitybetween respective colors that is caused depending on an F-number of theon-chip lens 22.

It is to be noted that in the photoelectric conversion element 10according to the present embodiment, signal electric charges (electrons)are extracted from the lower electrode 15 a; therefore, in thesolid-state imaging device using the photoelectric conversion element 10as each of the pixels, the upper electrode 18 may be a common electrode.In this case, a transmission path including the contact hole H, thecontact metal layer 20, the wiring layers 15 b and 13 b, the conductiveplugs 120 b 1 and 120 b 2 mentioned above may be formed at least at oneposition for all pixels.

In the semiconductor substrate 11, for example, the inorganicphotoelectric converters 11B and 11R and the green electric storagelayer 110G are so formed as to be embedded in a predetermined region ofthe n-type silicon (Si) layer 110. Moreover, the conductive plugs 120 a1 and 120 b 1 configuring a transmission path of electric charges(electrons or holes (holes)) from the organic photoelectric converter11G are embedded in the semiconductor substrate 11. In the presentembodiment, a back surface (the surface 51) of the semiconductorsubstrate 11 serves as a light reception surface. A plurality of pixeltransistors (including transfer transistors Tr1 to Tr3) corresponding tothe organic photoelectric converter 11G and the inorganic photoelectricconverters 11B and 11R, and a peripheral circuit including a logiccircuit, etc. are formed on a side on which the front surface (thesurface S2) is located of the semiconductor substrate 11.

Examples of the pixel transistor include a transfer transistor, a resettransistor, an amplification transistor, and a selection transistor.Each of these pixel transistors includes, for example, a MOS transistor,and is formed in a p-type semiconductor well region on a side on whichthe surface S2 is located. A circuit including such pixel transistors isformed for each of photoelectric converters of red, green, and blue.Each of the circuits may have, for example, a three-transistorconfiguration including three transistors in total, i.e., the transfertransistor, the reset transistor, and the amplification transistor outof these pixel transistors, or may have, for example, a four-transistorconfiguration further including the selection transistor in addition tothe three transistors mentioned above. Only the transfer transistors Tr1to Tr3 of these pixel transistors are illustrated and describedhereinbelow. Moreover, it is possible to share the pixel transistorsother than the transfer transistor among the photoelectric converters oramong the pixels. Further, a so-called pixel sharing configuration inwhich a floating diffusion is shared is applicable.

The transfer transistors Tr1 to Tr3 include gate electrodes (gateelectrodes TG1 to TG3) and floating diffusions (FD 113, 114, and 116).The transfer transistor Tr1 transfers, to a vertical signal line Lsig tobe described later, signal electric charges (electrons in the presentembodiment) corresponding to green that are generated in the organicphotoelectric converter 11G and stored in the green electric storagelayer 110G. The transfer transistor Tr2 transfers, to the verticalsignal line Lsig to be described later, signal electric charges(electrons in the present embodiment) corresponding to blue that aregenerated and stored in the inorganic photoelectric converter 11B.Likewise, the transfer transistor Tr3 transfers, to the vertical signalline Lsig to be described later, signal electric charges (electrons inthe present embodiment) corresponding to red that are generated andstored in the inorganic photoelectric converter 11R.

The inorganic photoelectric converters 11B and 11R are each a photodiodehaving a p-n junction, and are formed in an optical path in thesemiconductor substrate 11 in this order from the surface S1. Theinorganic photoelectric converter 11B of the inorganic photoelectricconverters 11B and 11R selectively detects blue light and stores signalelectric charges corresponding to blue, and is so formed as to extend,for example, from a selective region along the surface S1 of thesemiconductor substrate 11 to a region in proximity to an interface withthe multilayer wiring layer 51. The inorganic photoelectric converter11R selectively detects red light and stores signal electric chargescorresponding to red, and is formed, for example, in a region below theinorganic photoelectric converter 11B (closer to the surface S2). It isto be noted that blue (B) and red (R) are, for example, a colorcorresponding to a wavelength region from 450 nm to 495 nm bothinclusive and a color corresponding to a wavelength region from 620 nmto 750 nm both inclusive, respectively, and each of the inorganicphotoelectric converters 11B and 11R may be allowed to detect light ofpart or the entirety of the relevant wavelength region.

FIG. 3(A) illustrates specific configuration examples of the inorganicphotoelectric converters 11B and 11R. FIG. 3(B) corresponds to aconfiguration in other cross-section of FIG. 3(A). It is to be notedthat in the present embodiment, description is given of a case whereelectrons of electron-hole pairs generated by photoelectric conversionare read as signal electric charges (a case where an n-typesemiconductor region serves as a photoelectric conversion layer).Moreover, in the drawings, a superscript “+(plus)” placed at “p” or “n”indicates that p-type or n-type impurity concentration is high. Further,gate electrodes TG2 and TG3 of the transfer transistors Tr2 and Tr3 outof the pixel transistors are also illustrated.

The inorganic photoelectric converter 11B includes, for example, ap-type semiconductor region (hereinafter simply referred to as p-typeregion, an n-type semiconductor region is referred in a similar manner)111 p serving as a hole storage layer and an n-type photoelectricconversion layer (an n-type region) 111 n serving as an electron storagelayer. The p-type region 111 p and the n-type photoelectric conversionlayer 111 n are formed in respective selective regions in proximity tothe surface S1, and are bent and extend to allow a portion thereof toreach an interface with the surface S2. The p-type region 111 p iscoupled to an unillustrated p-type semiconductor well region on a sideon which the surface S1 is located. The n-type photoelectric conversionlayer 111 n is coupled to the FD 113 (an n-type region) of the transfertransistor Tr2 for blue. It is to be noted that a p-type region 113 p (ahole storage layer) is formed in proximity to an interface between eachof ends on the side on which the surface S2 is located of the p-typeregion 111 p and the n-type photoelectric conversion layer 111 n and thesurface S2.

The inorganic photoelectric converter 11R is formed, for example, bysandwiching an n-type photoelectric conversion layer 112 n (an electronstorage layer) between the p-type regions 112 p 1 and 112 p 2 (holestorage layers) (that is, has a p-n-p laminated structure). The n-typephotoelectric conversion layer 112 n is bent and extends to allow aportion thereof to reach an interface with the surface S2. The n-typephotoelectric conversion layer 112 n is coupled to the FD 114 (an n-typeregion) of the transfer transistor Tr3 for red. It is to be noted that ap-type region 113 p (a hole storage layer) is formed at least inproximity to an interface between the end on the side on which thesurface S2 is located of the n-type photoelectric conversion layer 111 nand the surface S2.

FIG. 4 illustrates a specific configuration example of the greenelectric storage layer 110G. It is to be noted that hereinafter,description is given of a case where electrons of electrons-hole pairsgenerated by the organic photoelectric converter 11G are read as signalelectric charges from the lower electrode 15 a. Moreover, the gateelectrode TG1 of the transfer transistor Tr1 out of the pixeltransistors is also illustrated in FIG. 4 .

The green electric storage layer 110G includes an n-type region 115 nserving as an electron storage layer. A portion of the n-type region 115n is coupled to the conductive plug 120 a 1, and stores electronstransmitted from the lower electrode 15 a through the conductive plug120 a 1. The n-type region 115 n is also coupled to the FD 116 (ann-type region) of the transfer transistor Tr1 for green. It is to benoted that a p-type region 115 p (a hole storage layer) is formed inproximity to an interface between the n-type region 115 n and thesurface S2.

The conductive plugs 120 a 1 and 120 b 2 serve as connectors between theorganic photoelectric converter 11G and the semiconductor substrate 11together with the conductive plugs 120 a 2 and 120 a 2 to be describedlater, and configure a transmission path of electrons or holes generatedin the organic photoelectric converter 11G. In the present embodiment,the conductive plug 120 a 1 is brought into conduction with the lowerelectrode 15 a of the organic photoelectric converter 11G, and iscoupled to the green electric storage layer 110G. The conductive plug120 b 1 is brought into conduction with the upper electrode 18 of theorganic photoelectric converter 11G, and serves as a wiring line fordischarge of holes.

Each of the conductive plugs 120 a 1 and 120 b 1 includes, for example,a conductive semiconductor layer, and is so formed as to be embedded inthe semiconductor substrate 11. In this case, the conductive plug 120 a1 is of an n type (to serve as an electron transmission path), and theconductive plug 120 b 1 may be of a p type (to serve as a holetransmission path). Alternatively, each of the conductive plugs 120 a 1and 120 b 1 may be, for example, a conductive film material such astungsten contained in a through via. In this case, for example, tosuppress a short circuit with silicon, it is desirable to cover a viaside surface with an insulating film including silicon oxide (SiO₂),silicon nitride (SiN), or the like.

The multilayer wiring layer 51 is formed on the surface S2 of thesemiconductor substrate 11. In the multilayer wiring layer 51, aplurality of wiring lines 51 a are provided with an interlayerinsulating film 52 in between. As described above, in the photoelectricconversion element 10, the multilayer wiring layer 51 is formed on aside opposite to the light reception surface, which makes it possible toachieve a so-called back-side illumination type solid-state imagingdevice. For example, a supporting substrate 53 including silicon isbonded to the multilayer wiring layer 51.

(1-2. Method of Manufacturing Photoelectric Conversion Element)

It is possible to manufacture the photoelectric conversion element 10 asfollows, for example. FIGS. 5A to 7C illustrate a method ofmanufacturing the photoelectric conversion element 10 in process order.It is to be noted that FIGS. 7A to 7C illustrate only a main-partconfiguration of the photoelectric conversion element 10. It is to benoted that a method of fabricating the photoelectric conversion element10 to be described below is merely an example, and the method offabricating the photoelectric conversion element 10 (and a photoelectricconversion element 30 to be described later) according to the embodimentof the present disclosure is not limited to the following example.

First, the semiconductor substrate 11 is formed. Specifically, aso-called SOI substrate is prepared. In the SOI substrate, the siliconlayer 110 is formed on a silicon base 1101 with a silicon oxide film1102 in between. It is to be noted that a surface on a side on which thesilicon oxide film 1102 is located, of the silicon layer 110 serves asthe back surface (the surface 51) of the semiconductor substrate 11.FIGS. 5A and 5B illustrate a state in which a configuration illustratedin FIG. 1 is vertically inverted. Next, the conductive plugs 120 a 1 and120 b 1 are formed in the silicon layer 110, as illustrated in FIG. 5A.At this occasion, for example, through vias are formed in the siliconlayer 110, and thereafter, a barrier metal such as silicon nitridedescribed above and tungsten are contained in the through vias, whichmakes it possible to form the conductive plugs 120 a 1 and 120 b 1.Alternatively, a conductive impurity semiconductor layer may be formedby, for example, ion implantation on the silicon layer 110. In thiscase, the conductive plug 120 a 1 is formed as an n-type semiconductorlayer, and the conductive plug 120 b 1 is formed as a p-typesemiconductor layer. Thereafter, the inorganic photoelectric converters11B and 11R each having, for example, the p-type region and the n-typeregion as illustrated in FIG. 3A are formed by ion implantation inregions located at depths different from each other in the silicon layer110 (to be superimposed on each other). Moreover, the green electricstorage layer 110G is formed by ion implantation in a region adjacent tothe conductive plug 120 a 1. Thus, the semiconductor substrate 11 isformed.

Subsequently, the pixel transistors including the transfer transistorsTr1 to Tr3 and peripheral circuits such as a logic circuit are formed onthe side on which the surface S2 is located of the semiconductorsubstrate 11, and thereafter, a plurality of layers of wiring lines 51 aare formed on the surface S2 of the semiconductor substrate 11 with theinterlayer insulating film 52 in between to form the multilayer wiringlayer 51, as illustrated in FIG. 5B. Next, the supporting substrate 53including silicon is bonded onto the multilayer wiring layer 51, andthereafter, the silicon base 1101 and the silicon oxide film 1102 areremoved from the surface 51 of the semiconductor substrate 11 to exposethe surface 51 of the semiconductor substrate 11.

Next, the organic photoelectric converter 11G is formed on the surface51 of the semiconductor substrate 11. Specifically, first, theinterlayer insulating film 12 that includes the foregoing laminated filmincluding the hafnium oxide film and the silicon oxide film is formed onthe surface 51 of the semiconductor substrate 11, as illustrated in FIG.6A. For example, after the hafnium oxide film is formed by an ALD(atomic layer deposition) method, the silicon oxide film is formed by,for example, a plasma CVD (Chemical Vapor Deposition) method.Thereafter, the contact holes H1 a and H1 b are formed at positionsfacing the conductive plugs 120 a 1 and 120 b 1 of the interlayerinsulating film 12, and the conductive plugs 120 a 2 and 120 b 2including the foregoing material are formed so as to be contained in thecontact holes H1 a and H1 b, respectively. At this occasion, theconductive plugs 120 a 2 and 120 b 2 may be formed to protrude to aregion to be light-blocked (to cover the region to be light-blocked), ora light-blocking layer may be formed in a region isolated from theconductive plugs 120 a 2 and 120 b 2.

Subsequently, the interlayer insulating film 14 including the foregoingmaterial is formed by, for example, a plasma CVD method, as illustratedin FIG. 6B. It is to be noted that after film formation, a front surfaceof the interlayer insulating film 14 is desirably planarized by, forexample, a CMP (Chemical Mechanical Polishing) method. Next, contactholes are formed at positions facing the conductive plugs 120 a 2 and120 b 2 of the interlayer insulating film 14, and the contact holes arefilled with the foregoing material to form the wiring layers 13 a and 13b. It is to be noted that, thereafter, a surplus wiring layer material(such as tungsten) on the interlayer insulating film 14 is desirablyremoved by a CMP method, etc. Next, the lower electrode 15 a is formedon the interlayer insulating film 14. Specifically, first, the foregoingtransparent conductive film is formed on the entire surface of theinterlayer insulating film 14 by, for example, a sputtering method.Thereafter, a selective portion is removed with use of aphotolithography method (through performing light exposure, development,post-baking, etc. on a photoresist film), for example, with use of dryetching or wet etching to form the lower electrode 15 a. At thisoccasion, the lower electrode 15 a is formed in a region facing thewiring layer 13 a. Moreover, in processing of the transparent conductivefilm, the transparent conductive film remains also in a region facingthe wiring layer 13 b to form, together with the lower electrode 15 a,the wiring layer 15 b configuring a portion of a hole transmission path.

Subsequently, the insulating film 16 is formed. At this occasion, first,the insulating film 16 including the foregoing material is formed by,for example, a plasma CVD method on the entire surface of thesemiconductor substrate 11 to cover the interlayer insulating film 14,the lower electrode 15 a, and the wiring layer 15 b. Thereafter, theformed insulating film 16 is polished by, for example, a CMP method toexpose the lower electrode 15 a and the wiring layer 15 b from theinsulating film 16 and to reduce (desirably eliminate) a difference inlevel between the lower electrode 15 a and the insulating film 16, asillustrated in FIG. 7A.

Next, the organic photoelectric conversion layer 17 is formed on thelower electrode 15 a, as illustrated in FIG. 7B. At this occasion,pattern formation of the HR-type quinacridone derivative and thesubphthalocyanine derivative mentioned above is performed by, forexample, a vacuum deposition method. It is to be noted that in a casewhere another organic layer (such as an electron blocking layer) isformed above or below the organic photoelectric conversion layer 17 asdescribed above, the organic layer is desirably formed continuously in avacuum process (in-situ vacuum process). Moreover, the method of formingthe organic photoelectric conversion layer 17 is not necessarily limitedto a technique using the foregoing vacuum deposition method, and anyother technique, for example, a print technology may be used.

Subsequently, the upper electrode 18 and the protective layer 19 areformed, as illustrated in FIG. 7C. First, the upper electrode 18including the foregoing transparent conductive film is formed on anentire substrate surface by, for example, a vacuum deposition method ora sputtering method to cover a top surface and a side surface of theorganic photoelectric conversion layer 17. It is to be noted thatcharacteristics of the organic photoelectric conversion layer 17 easilyvary by an influence of water, oxygen, hydrogen, etc.; therefore, theupper electrode 18 is desirably formed by an in-situ vacuum processtogether with the organic photoelectric conversion layer 17. Thereafter(before pattering the upper electrode 18), the protective layer 19including the foregoing material is formed by, for example, a plasma CVDmethod to cover a top surface of the upper electrode 18. Subsequently,after the protective layer 19 is formed on the upper electrode 18, theupper electrode 18 is processed.

Thereafter, selective portions of the upper electrode 18 and theprotective layer 19 are collectively removed by etching using aphotolithography method. Subsequently, the contact hole H is formed inthe protective layer 19 by, for example, etching using aphotolithography method. At this occasion, the contact hole H isdesirably formed in a region not facing the organic photoelectricconversion layer 17. Even after formation of the contact hole H, aphotoresist is removed, and cleaning using a chemical solution isperformed by a method similar to the foregoing method; therefore, theupper electrode 18 is exposed from the protective layer 19 in a regionfacing the contact hole H. Accordingly, in view of generation of a pinhole as described above, the contact hole H is desirably provided in aregion other than a region where the organic photoelectric conversionlayer 17 is formed. Subsequently, the contact metal layer 20 includingthe foregoing material is formed with use of, for example, a sputteringmethod, etc. At this occasion, the contact metal layer 20 is formed onthe protective layer 19 to be contained in the contact hole H and extendto a top surface of the wiring layer 15 b. Lastly, the planarizationlayer 21 is formed on the entire surface of the semiconductor substrate11, and thereafter, the on-chip lens 22 is formed on the planarizationlayer 21. Thus, the photoelectric conversion element 10 illustrated inFIG. 1 is completed.

In the foregoing photoelectric conversion element 10, for example, asthe pixel of the solid-state imaging device, signal electric charges areobtained as follows. More specifically, as illustrated in FIG. 8 , lightL enters the photoelectric conversion element 10 through the on-chiplens 22 (not illustrated in FIG. 8 ), and thereafter, the light L passesthrough the organic photoelectric converter 11G and the inorganicphotoelectric converters 11B and 11R in this order. Each of green light,blue light, and red light of the light L is subjected to photoelectricconversion in the course of passing. FIG. 9 schematically illustrates aflow of obtaining signal electric charges (electrons) on the basis ofincident light. Hereinafter, description is given of a specific signalobtaining operation in each photoelectric converter.

(Obtaining of Green Signal by Organic Photoelectric Converter 11G)

First, green light Lg of the light L having entered the photoelectricconversion element 10 is selectively detected (absorbed) by the organicphotoelectric converter 11G to be subjected to photoelectric conversion.Electrons Eg of thus-generated electron-hole pairs are extracted fromthe lower electrode 15 a, and thereafter, the electrons Eg are stored inthe green electric storage layer 110G through a transmission path A (thewiring layer 13 a and the conductive plugs 120 a 1 and 120 a 2). Thestored electrons Eg are transferred to the FD 116 in a readingoperation. It is to be noted that holes Hg are discharged from the upperelectrode 18 through a transmission path B (the contact metal layer 20,the wiring layers 13 b and 15 b, and the conductive plugs 120 b 1 and120 b 2).

Specifically, the signal electric charges are stored as follows. Namely,in the present embodiment, a predetermined negative potential VL (<0 V)and a potential VU (<VL) lower than the potential VL are applied to thelower electrode 15 a and the upper electrode 18, respectively. It is tobe noted that the potential VL are applied to the lower electrode 15 afrom, for example, the wiring line 51 a in the multilayer wiring layer51 through the transmission path A. The potential VL is applied to theupper electrode 18 from, for example, the wiring line 51 a in themultilayer wiring layer 51 through the transmission path B. Thus, in anelectric charge storing state (an OFF state of the unillustrated resettransistor and the transfer transistor Tr1), electrons of theelectron-hole pairs generated in the organic photoelectric conversionlayer 17 are guided to the lower electrode 15 a having a relatively highpotential (holes are guided to the upper electrode 18). Thus, theelectrons Eg are extracted from the lower electrode 15 a to be stored inthe green electric storage layer 110G (specifically, the n-type region115 n) through the transmission path A. Moreover, storage of theelectrons Eg changes the potential VL of the lower electrode 15 abrought into conduction with the green electric storage layer 110G. Achange amount of the potential VL corresponds to a signal potential(herein, a potential of a green signal).

Moreover, in a reading operation, the transfer transistor Tr1 is turnedto an ON state, and the electrons Eg stored in the green electricstorage layer 110G are transferred to the FD 116. Accordingly, a greensignal based on a light reception amount of the green light Lg is readto the vertical signal line Lsig to be described later through anunillustrated other pixel transistor. Thereafter, the unillustratedreset transistor and the transfer transistor Tr1 are turned to an ONstate, and the FD 116 as the n-type region and a storage region (then-type region 115 n) of the green electric storage layer 110G are resetto, for example, a power source voltage VDD.

(Obtaining of Blue Signal and Red Signal by Inorganic PhotoelectricConverters 11B and 11R)

Next, blue light and red light of light having passed through theorganic photoelectric converter 11G are absorbed in order by theinorganic photoelectric converter 11B and the inorganic photoelectricconverter 11R, respectively, to be subjected to photoelectricconversion. In the inorganic photoelectric converter 11B, electrons Ebcorresponding to the blue light having entered the inorganicphotoelectric converter 11B are stored in the n-type region (the n-typephotoelectric conversion layer 111 n), and the stored electrons Ed aretransferred to the FD 113 in the reading operation. It is to be notedthat holes are stored in an unillustrated p-type region. Likewise, inthe inorganic photoelectric converter 11R, electrons Er corresponding tothe red light having entered the inorganic photoelectric converter 11Rare stored in the n-type region (the n-type photoelectric conversionlayer 112 n), and the stored electrons Er are transferred to the FD 114in the reading operation. It is to be noted that holes are stored in anunillustrated p-type region.

In the electric charge storing state, the negative potential VL isapplied to the lower electrode 15 a of the organic photoelectricconverter 11G, as described above, which causes a tendency to increasehole concentration in the p-type region (the p-type region 111 p in FIG.2 ) as a hole storage layer of the inorganic photoelectric converter11B. This makes it possible to suppress generation of a dark current atan interface between the p-type region 111 p and the interlayerinsulating film 12.

In the reading operation, as with the foregoing organic photoelectricconverter 11G, the transfer transistors Tr2 and Tr3 are turned to an ONstate, and the electrons Eb stored in the n-type photoelectricconversion layer 111 n and the electrons Er stored in the n-typephotoelectric conversion layer 112 n are transferred to the FDs 113 and114, respectively. Accordingly, each of a blue signal based on a lightreception amount of the blue light Lb and a red signal based on a lightreception amount of the red light Lr is read to the vertical signal lineLsig to be described later through an unillustrated other pixeltransistor. Thereafter, the unillustrated reset transistor and thetransfer transistors Tr2 and Tr3 are turned to the ON state, and the FDs113 and 114 as the n-type regions are reset to, for example, the powersource voltage VDD.

As described above, the organic photoelectric converter 11G and theinorganic photoelectric converters 11B and 11R are stacked along thevertical direction, which makes it possible to separately detect redlight, green light, and blue light without providing a color filter,thereby obtaining signal electric charges of respective colors. Thismakes it possible to suppress light loss (reduction in sensitivity)resulting from color light absorption by the color filter and generationof false color associated with pixel interpolation processing.

(1-3. Workings and Effects)

A typical solid-state imaging device adopts, for example, a so-calledbulk-hetero structure in which a photoelectric converter (an organicphotoelectric converter) including an organic material and an inorganicphotoelectric converter including an inorganic material such as Si arestacked. In this solid-state imaging device, co-evaporation of theorganic p-type organic semiconductor material and the organic n-typeorganic semiconductor material in the organic photoelectric convertermakes it possible to increase an electric charge separation interface,thereby achieving high conversion efficiency. In recent years, asdescribed above, in solid-state imaging devices such as CCD imagesensors and CMOS image sensors, high color reproducibility, a high framerate, and high sensitivity have been in demand, and the spectroscopicshape has been further improved, and responsivity and external quantumefficiency have been improved.

Various imaging devices have been developed in order to achieve asuperior spectroscopic shape, high responsivity, and high externalquantum efficiency, and in particular, a photoelectric conversionelement using a quinacridone derivative is expected. For example, in aphotoelectric conversion element using a combination of a quinacridonederivative and a subphthalocyanine derivative, a superior spectroscopicshape and high external quantum efficiency are confirmed. However, it isdifficult to achieve three characteristics, that is, the spectroscopicshape, responsivity, and external quantum efficiency. In the foregoingphotoelectric conversion element using the combination of thequinacridone derivative and the subphthalocyanine derivative, thespectroscopic shape and external quantum efficiency are improved, but asufficient characteristic related to responsivity is not achieved.

In contrast, in the present embodiment, the organic photoelectricconversion layer 17 is formed using the quinacridone derivativerepresented by the foregoing formula (1). This quinacridone derivativerepresented by the formula (1) is the HR-type quinacridone derivative inwhich one of two amine sites in a molecule is secondary amine (NHRR′)and the other is tertiary amine (NRR′R″).

The quinacridone derivative used in the foregoing photoelectricconversion element including the combination of the quinacridonederivative and the subphthalocyanine derivative is a so-called HH-typequinacridone derivative in which both two amine sites in a molecule aresecondary amine (NHRR′) or a so-called RR-type quinacridone derivativein which both two amine sites in a molecule are tertiary amine (NRR′R″).The HH-type quinacridone derivative generally has high crystallinity.Accordingly, heat resistance is superior, but a grain size formed in afilm such as a photoelectric conversion layer is large, whichdeteriorates carrier movement efficiency in an interface between grains.Accordingly, it is considered that it is difficult to improveresponsivity. The RR-type quinacridone derivative also has highcrystallinity, as with the HH-type quinacridone derivative. Accordingly,it is assumed that it is difficult to improve responsivity due to thesame reason as that in the HH-type quinacridone derivative.

In contrast, the HR-type quinacridone derivative has relatively smallcrystal grains (grains) to be formed in a film. Accordingly, carriersefficiently move in an interface between the grains. It is thereforeassumed that carrier transport performance in the organic photoelectricconversion layer 17 is improved and responsivity is improved. Moreover,a carrier trap derived from a gap between the grains is reduced, whichimproves carrier use efficiency.

As described above, in the photoelectric conversion element 10 accordingto the present embodiment, the organic photoelectric conversion layer 17is formed using the HR-type quinacridone derivative represented by theforegoing formula (1), which improves carrier transport performance anduse efficiency in the organic photoelectric conversion layer 17. Thismakes it possible to improve responsivity and external quantumefficiency while maintaining a sharp spectroscopic shape. In otherwords, it is possible to provide a photoelectric conversion elementachieving a superior spectroscopic shape, high responsivity, and highexternal quantum efficiency.

2. Second Embodiment

FIG. 10 illustrates a cross-sectional configuration of a photoelectricconversion element 30 according to a second embodiment of the presentdisclosure. The photoelectric conversion element 30 has across-sectional configuration similar to that of the photoelectricconversion element 10 according to the foregoing first embodiment, andconfigures, for example, one pixel in a solid-state imaging device (tobe described later) such as a CCD image sensor or a CMOS image sensor.In the photoelectric conversion element 30 according to the presentembodiment, an organic photoelectric conversion layer 37 configuring anorganic photoelectric converter 31G is formed using a quinacridonederivative (a second quinacridone derivative) represented by a formula(3) to be described later together with the HR-type quinacridonederivative represented by the foregoing formula (1). It is to be notedthat components same as those in the first embodiment are denoted by thesame reference numerals, and description of such components isappropriately omitted.

The organic photoelectric conversion layer 37 includes one or both of anorganic p-type semiconductor and an organic n-type semiconductor.Moreover, the organic photoelectric conversion layer 37 performsphotoelectric conversion on light in a selective wavelength region(herein, light within a range from 450 nm to 650 nm both inclusive), andallows light in other wavelength regions to pass therethrough. Theorganic photoelectric conversion layer 37 in the present embodiment isformed using two kinds of quinacridone derivatives. The two kinds ofquinacridone derivatives are the HR-type quinacridone derivativerepresented by the formula (1) and the quinacridone derivativerepresented by the following formula (3). The quinacridone derivativerepresented by the formula (3) is a so-called HH-type quinacridonederivative in which both two amine sites in a molecule are secondaryamine (NHRR′).

(where each of R16 and R17 is independently one of an alkyl group, analkenyl group, an alkynyl group, an aryl group, a cyano group, a nitrogroup, and a silyl group, each of n1 and n2 is independently 0 or aninteger of 1 or more, and in a case where each of n1 and n2 is 2 ormore, two or more R16 are optionally bound to one another to form a ringand two or more R17 are optionally bound to one another to form a ring.)

Specific examples of the quinacridone derivative represented by theforegoing formula (3) include compounds represented by the followingformulas (3-1) to (3-4), etc.

Moreover, the organic photoelectric conversion layer 37 preferablyincludes the subphthalocyanine derivative represented by the foregoingformula (2) together with the HR-type quinacridone derivative and theHH-type quinacridone derivative.

It is to be noted that in the present embodiment, each of the HR-typequinacridone derivative and the HH-type quinacridone derivativedescribed above serves as an organic p-type semiconductor, and theforegoing subphthalocyanine derivative serves as an organic n-typesemiconductor.

The organic photoelectric conversion layer 37 preferably includes theHR-type quinacridone derivative represented by the formula (1) and theHH-type quinacridone derivative represented by the foregoing formula (3)within, for example, a range from 25% to 75% both inclusive in volumeratio. A total content of the two kinds of quinacridone derivatives iswithin the foregoing range, which makes it possible to further improveexternal quantum efficiency in addition to an improvement inresponsivity. Moreover, as contents of the HR-type quinacridonederivative and the HH-type quinacridone derivative, the HR-typequinacridone derivative is preferably included within, for example, arange from 33% to 67% both inclusive in volume ratio. Including theHR-type quinacridone derivative within this range makes responsivity andexternal quantum efficiency compatible in a better balanced manner.

As described above, in the photoelectric conversion element 30 accordingto the present embodiment, the organic photoelectric conversion layer 37is formed using the HR-type quinacridone derivative and the HH-typequinacridone derivative represented by the foregoing formula (3). Thisimproves carrier use efficiency in the organic photoelectric conversionlayer 37, which achieves, in addition to the effects in the firstembodiment, an effect that it is possible to further improve externalquantum efficiency.

3. Application Examples Application Example 1

FIG. 11 illustrates an entire configuration of a solid-state imagingdevice (the solid-state imaging device 1) using the photoelectricconversion element 10 (or the photoelectric conversion element 30)described in the foregoing embodiments as each of the pixels. Thesolid-state imaging device 1 is a CMOS image sensor, and includes apixel section 1 a as an imaging region and a peripheral circuit section130 in a peripheral region of the pixel section 1 a on the semiconductorsubstrate 11. The peripheral circuit section 130 includes, for example,a row scanner 131, a horizontal selector 133, a column scanner 134, anda system controller 132.

The pixel section 1 a includes, for example, a plurality of unit pixelsP (each corresponding to the photoelectric conversion element 10) thatare two-dimensionally arranged in rows and columns. The unit pixels Pare wired with pixel driving lines Lread (specifically, row selectionlines and reset control lines) for respective pixel rows, and are wiredwith vertical signal lines Lsig for respective pixel columns. The pixeldriving lines Lread transmit drive signals for signal reading from thepixels. The pixel driving lines Lread each have one end coupled to acorresponding one of output terminals, corresponding to the respectiverows, of the row scanner 131.

The row scanner 131 is, for example, a pixel driver that includes ashift register, an address decoder, etc., and drives the unit pixels Pof the pixel section 1 a on a row basis. Signals outputted from the unitpixels P of a pixel row selected and scanned by the row scanner 131 aresupplied to the horizontal selector 133 through the respective verticalsignal lines Lsig. The horizontal selector 133 includes, for example, anamplifier, a horizontal selection switch, etc. that are provided foreach of the vertical signal lines Lsig.

The column scanner 134 includes a shift register, an address decoder,etc., and drives the horizontal selection switches of the horizontalselector 133 in order while sequentially performing scanning of thosehorizontal selection switches. Such selection and scanning performed bythe column scanner 134 allow the signals of the pixels transmittedthrough the respective vertical signal lines Lsig to be sequentiallyoutputted to a horizontal signal line 135. The thus-outputted signalsare transmitted to outside of the semiconductor substrate 11 through thehorizontal signal line 135.

A circuit portion including the row scanner 131, the horizontal selector133, the column scanner 134, and the horizontal signal line 135 may beprovided directly on the semiconductor substrate 11, or may be disposedin an external control IC. Alternatively, the circuit portion may beprovided in any other substrate coupled by means of a cable or the like.

The system controller 132 receives a clock supplied from the outside ofthe semiconductor substrate 11, data on instructions of operation modes,and the like, and outputs data such as internal information of thesolid-state imaging device 1. Furthermore, the system controller 132includes a timing generator that generates various timing signals, andperforms drive control of peripheral circuits such as the row scanner131, the horizontal selector 133, and the column scanner 134 on thebasis of the various timing signals generated by the timing generator.

Application Example 2

The foregoing solid-state imaging device 1 is applicable to variouskinds of electronic apparatuses having imaging functions. Examples ofthe electronic apparatuses include camera systems such as digital stillcameras and video cameras, and mobile phones having imaging functions.FIG. 12 illustrates, for purpose of an example, a schematicconfiguration of an electronic apparatus 2 (a camera). The electronicapparatus 2 is, for example, a video camera that allows for shooting ofa still image or a moving image. The electronic apparatus 2 includes thesolid-state imaging device 1, an optical system (an optical lens) 310, ashutter unit 311, a driver 313, and a signal processor 312. The driver313 drives the solid-state imaging device 1 and the shutter unit 311.

The optical system 310 guides image light (incident light) from anobject toward the pixel section 1 a of the solid-state imaging device 1.The optical system 310 may include a plurality of optical lenses. Theshutter unit 311 controls a period in which the solid-state imagingdevice 1 is irradiated with the light and a period in which the light isblocked. The driver 313 controls a transfer operation of the solid-stateimaging device 1 and a shutter operation of the shutter unit 311. Thesignal processor 312 performs various signal processes on signalsoutputted from the solid-state imaging device 1. A picture signal Douthaving been subjected to the signal processes is stored in a storagemedium such as a memory, or is outputted to a monitor or the like.

4. EXAMPLES

Hereinafter, various samples related to the first and second embodimentsof the present disclosure were fabricated, and external quantumefficiency (EQE) and responsivity of the samples were evaluated.

(Experiment 1)

First, as a sample 1-1, a glass substrate provided with an ITO electrodehaving a film thickness of 50 nm was cleaned by UV/ozone treatment, andthereafter, N-methylquinacridone (MMQD) represented by the formula (1-1)and chloroborane (2,3,9,10,16,17-hexafluorosubphthalocyanine)(F₆SubPcCl) represented by the formula (2-1) were concurrentlyevaporated on the glass substrate by a resistance heating method under areduced pressure of 1×10⁻⁵ Pa or less with use of an organic evaporationapparatus while rotating a substrate holder to form the organicphotoelectric conversion layer. Evaporation speeds of MMQD and F₆SubPcClwere 0.050 nm/sec and 0.050 nm/sec, respectively, and a film having atotal thickness of 100 nm was formed. Moreover, a film of AlSiCu wasformed as an upper electrode with a film thickness of 100 nm on theorganic photoelectric conversion layer to fabricate a photoelectricconversion element having a 1 mmxl mm photoelectric conversion region.

In addition, as samples 1-2 to 1-8, photoelectric conversion elementswere fabricated by a method similar to that in the sample 1-1, using, inplace of MMQD, quinacridone (QD; the sample 1-2) represented by theformula (3-1), 2,9-dimethylquinacridone (PR122; the sample 1-3)represented by the formula (3-2), 2,9-diethylquinacridone (EQD; thesample 1-4) represented by the formula (3-3),2,9-di-tert-butylquinacridone (BQD; the sample 1-5) represented by theformula (3-4), N,N′-dimethylquinacridone (DMQD; the sample 1-6)represented by the following formula (4-1), N,N′-diphenylquinacridone(DPQD; the sample 1-7) represented by the following formula (4-2), andN,N′-diphenyl-2,9-di-tert-butylquinacridone (BPQD; the sample 1-8)represented by a formula (4-3). External quantum efficiency (EQE) andresponsivity of the samples 1-1 to 1-7 were evaluated as follows. Table1 summarizes configurations of the organic photoelectric conversionlayers, types of quinacridone derivatives used for the organicphotoelectric conversion layers, and evaluation results of EQE andresponsivity in the sample 1-1 to 1-7. It is to be noted that each ofthe evaluation results of EQE and responsivity is a relative value withreference to the result in the sample 1-1 as a reference value.

(Method of Evaluating External Quantum Efficiency)

External quantum efficiency was evaluated with use of a semiconductorparameter analyzer. Specifically, external quantum efficiency wascalculated from a bright current value and a dark current value in acase where an amount of light to be applied from a light source to thephotoelectric conversion element through a filter was 1.62 μW/cm², and abias voltage to be applied between electrodes was −1 V.

(Method of Evaluating Responsivity)

Responsivity was evaluated by measuring speed of falling, after stoppingapplication of light, a bright current value observed during applicationof light with use of a semiconductor parameter analyzer. Specifically,an amount of light to be applied from a light source to thephotoelectric conversion element through a filter was 1.62 μW/cm², and abias voltage to be applied between electrodes was −1 V. A stationarycurrent was observed in this state, and thereafter, application of lightwas stopped, and how the current was attenuated was observed.Subsequently, a dark current value was subtracted from an obtainedcurrent-time curve. A current-time curve to be thereby obtained wasused, and time necessary for a current value after stopping applicationof light to attenuate to 3% of an observed current value in a stationarystate was an indication of responsivity.

TABLE 1 Configuration of Type of Photoelectric QD Conversion Layerderivative EQE Responsivity Sample 1-1 Formula (1-1) Formula (2-1) HR1.0 1.0 Sample 1-2 Formula (3-1) Formula (2-1) HH 2.1 8.0 Sample 1-3Formula (3-2) Formula (2-1) HH 1.9 7.6 Sample 1-4 Formula (3-3) Formula(2-1) HH 2.3 5.0 Sample 1-5 Formula (3-4) Formula (2-1) HH 2.2 4.0Sample 1-6 Formula (4-1) Formula (2-1) RR 0.9 2.0 Sample 1-7 Formula(4-2) Formula (2-1) RR 0.2 2.0 Sample 1-8 Formula (4-3) Formula (2-1) RR0.6 8.0

As can be seen from Table 1, as compared with the sample 1-1 using theHR-type quinacridone derivative as the quinacridone derivativeconfiguring the organic photoelectric conversion layer, in the samples1-2 to 1-5 using the HH-type quinacridone derivative, external quantumefficiency was higher than that in the sample 1-1, but a large increasesin the falling time, that is, a large deterioration in responsivity wasobserved. Moreover, in the samples 1-6 to 1-8 using the RR-typequinacridone derivative as the quinacridone derivative configuring theorganic photoelectric conversion layer, both external quantum efficiencyand responsivity were lower than those in the sample 1-1. Therefore, itwas found that using the HR-type quinacridone derivative as thequinacridone derivative configuring the organic photoelectric conversionlayer made external quantum efficiency and responsivity compatible.

(Experiment 2)

Next, photoelectric conversion elements (samples 2-1 to 2-6) werefabricated by a method similar to that in the foregoing experiment 1except for the configuration of the organic photoelectric conversionlayer, and external quantum efficiency (EQE) and responsivity of thesesamples were evaluated. As quinacridone derivatives used in therespective samples, MMQD represented by the formula (1-1) was used inthe samples 2-1 and 2-2, QD represented by the formula (3-1) was used inthe samples 2-3 and 2-4, and DMQD represented by the formula (4-1) wasused in the samples 2-5 and 2-6. Moreover, as subphthalocyaninederivatives used for the respective samples, SubPsCl represented by theformula (2-3) was used in the samples 2-1, 2-3, and 2-5, andF₆SubPs-OPheCl represented by the formula (2-2) was used in the samples2-2, 2-4, and 2-6. Table 2 summarizes configurations of the organicphotoelectric conversion layers, types of quinacridone derivatives usedfor the organic photoelectric conversion layers, and evaluation resultsof EQE and responsivity in the sample 2-1 to 2-6. It is to be noted thateach of the evaluation results of EQE and responsivity is a relativevalue with reference to the result in the sample 2-1 as a referencevalue.

TABLE 2 Configuration of Type of Photoelectric QD Conversion Layerderivative EQE Responsivity Sample 2-1 Formula (1-1) Formula (2-3) HR1.0 1.0 Sample 2-2 Formula (1-1) Formula (2-2) HR 1.2 0.6 Sample 2-3Formula (3-1) Formula (2-3) HH 2.4 10 Sample 2-4 Formula (3-1) Formula(2-2) HH 2.4 8 Sample 2-5 Formula (4-1) Formula (2-3) RR 0.2 4 Sample2-6 Formula (4-1) Formula (2-2) RR 0.2 5

As can be seen from Table 2, the quinacridone derivative configuring theorganic photoelectric conversion layer had a tendency similar to theresults in the experiment 1 irrespective of the kind of thesubphthalocyanine derivative used together. In other words, as comparedwith the samples 2-1 and 2-2 using the HR-type quinacridone derivativeas the quinacridone derivative configuring the organic photoelectricconversion layer, in the samples 2-3 and 2-4 using the HH-typequinacridone derivative, quantum efficiency was higher than that in thesample 2-1, but a large deterioration in responsivity was observed.Moreover, in the samples 2-5 and 2-6 using the RR-type quinacridonederivative as the quinacridone derivative configuring the organicphotoelectric conversion layer, both external quantum efficiency andresponsivity were lower than those in the samples 2-1 and 2-2.

(Experiment 3)

Next, photoelectric conversion elements (samples 3-1 to 3-12) werefabricated by a method similar to that in the foregoing experiment 1except for the configuration of the organic photoelectric conversionlayer, and external quantum efficiency and responsivity of these sampleswere evaluated. In the present experiment, the organic photoelectricconversion layer included two kinds of quinacridone derivatives and asubphthalocyanine derivative.

As a first type of quinacridone derivative used in the respectivesamples, MMQD represented by the formula (1-1) was used in the samples3-1, 3-5, and 3-6, N-methyl-2,9-dimethylquinacridone (TMQD) representedby the formula (1-5) was used in the sample 3-2,N-methyl-2,9-di-tert-butylquinacridone (BMQD) represented by the formula(1-7) was used in the sample 3-3, and N-phenylquinacridone (MPQD)represented by the formula (1-3) was used in the samples 3-4 and 3-7.Moreover, DMQD represented by the formula (4-1) was used in the samples3-8 and 3-9, DPQD represented by the formula (4-2) was used in thesample 3-10, BQD represented by the formula (3-4) was used in the sample3-11, PR122 represented by the formula (3-2) was used in the sample3-12, and EQD represented by the formula (3-3) was used in the sample3-13. As a second type of quinacridone derivative, BQD represented bythe formula (3-4) was used. As the subphthalocyanine derivative,F₆SubPcCl represented by the formula (2-1) was used in the samples 3-1to 3-4 and 3-6 to 3-13, except that F₆SubPs-OPhCl represented by theformula (2-2) was used in the sample 3-5. It is to be noted that in eachof the samples 3-6 to 3-8, and 3-10, the second type of quinacridonederivative was not used to form the organic photoelectric conversionlayer. Table 3 summarizes configurations of the organic photoelectricconversion layers, types of quinacridone derivatives used for theorganic photoelectric conversion layers, and evaluation results of EQEand responsivity in the sample 3-1 to 3-13. It is to be noted that eachof the evaluation results of EQE and responsivity is a relative valuewith reference to the result in the sample 3-1 as a reference value.

TABLE 3 Type of QD Configuration of Photoelectric Conversion Layerderivative EQE Responsivity Sample 3-1 Formula (1-1) Formula (3-4)Formula (2-1) HR + HH 1.0 1.0 Sample 3-2 Formula (1-5) Formula (3-4)Formula (2-1) HR + HH 1.0 3.5 Sample 3-3 Formula (1-7) Formula (3-4)Formula (2-1) HR + HH 0.6 2.0 Sample 3-4 Formula (1-3) Formula (3-4)Formula (2-1) HR + HH 0.4 4.0 Sample 3-5 Formula (1-1) Formula (3-4)Formula (2-2) HR + HH 0.9 2.5 Sample 3-6 Formula (1-1) — Formula (2-1)HR 0.4 2.5 Sample 3-7 Formula (1-3) — Formula (2-1) HR 0.1 4.1 Sample3-8 Formula (4-1) — Formula (2-1) RR 0.4 5.0 Sample 3-9 Formula (4-1)Formula (3-4) Formula (2-1) RR + HH 0.5 7.0 Sample 3-10 Formula (4-2)Formula (3-4) Formula (2-1) RR + HH 0.1 30 Sample 3-11 Formula (3-4) —Formula (2-1) HH 0.9 10 Sample 3-12 Formula (3-2) Formula (3-4) Formula(2-1) HH + HH 0.9 17 Sample 3-13 Formula (3-3) Formula (3-4) Formula(2-1) HH + HH 1.0 11

The following was found from Table 3. First, it was found that in thesamples 3-1 to 3-5 in which the organic photoelectric conversion layerwas formed using the HR-type quinacridone derivative and the HH-typequinacridone derivative, high EQE was obtained, as compared with thesamples 3-6 and 3-7 using only the HR-type quinacridone derivative.Moreover, it was found that in the samples 3-1 to 3-5, high EQE andsuperior responsivity were obtained, as compared with the samples 3-9and 3-10 in which the organic photoelectric conversion layer was formedusing the RR-type quinacridone derivative and the HH-type quinacridonederivative. Further, as compared with the samples 3-12 and 3-13 in whichthe organic photoelectric conversion layer was formed using two kinds ofHH-type quinacridone derivatives, there was little difference in EQE,but responsivity was largely improved. Accordingly, it was found thatforming the organic photoelectric conversion layer using the HR-typequinacridone derivative and the HH-type quinacridone derivative madeexternal quantum efficiency and responsivity compatible and made itpossible to further improve external quantum efficiency.

It is to be noted that the sample 3-4 had less favorable results of EQEand responsivity, as compared with the samples 3-1 to 3-3. The followingreason is considered. For example, since EQE and responsivity in thesample 3-10 were deteriorated more than those in the sample 3-9, it isconsidered that a quinacridone derivative including a phenyl group as asubstituent group at an N-position has a tendency that EQE andresponsivity are deteriorated, as compared with a quinacridonederivative including a methyl group as the substituent group at theN-position. This tendency was shown between the samples 3-6 and thesamples 3-7 using the HR-type quinacridone derivative; therefore, it isconsidered that deteriorations in EQE and responsivity in the sample 3-4as compared with the samples 3-1 to 3-3 were caused by the substituentgroup at the N-position of the quinacridone derivative (a differencebetween the methyl group and the phenyl group). It is considered that acause of deteriorations in EQE and responsivity by conversion of thesubstituent group at the N-position of the quinacridone derivative fromthe methyl group to the phenyl group was that carrier transportperformance and carrier use efficiency were deteriorated by an influenceof the substituent group.

It is to be noted that in a case where the sample 3-4 (the HR-type+theHH-type) and the sample 3-7 (the HH-type) both using the MPQDrepresented by the formula (1-3) are compared with each other, in thesample 3-4, an improvement in EQE was observed without a deteriorationin responsivity. Accordingly, it is found that using the HH-typequinacridone derivative together with the HR-type quinacridonederivative makes EQE and responsivity compatible and makes it possibleto further improve EQE.

(Experiment 4)

Next, photoelectric conversion elements (samples 4-1 to 4-9) werefabricated by a method similar to that in the foregoing experiment 1except for the configuration of the organic photoelectric conversionlayer, and external quantum efficiency and responsivity of these sampleswere evaluated. In the present experiment, a volume ratio of thequinacridone derivative and the subphthalocyanine derivative configuringthe organic photoelectric conversion layer was verified.

In the samples 4-1 to 4-5, MMQD represented by the formula (1-1) as thequinacridone derivative and SubPcCl represented by the formula (2-3) asthe subphthalocyanine derivative were used. In the samples 4-6 to 4-8,QD represented by the formula (3-1) as the quinacridone derivative andSubPcCl represented by the formula (2-3) as the subphthalocyaninederivative were used. In the sample 4-9, DMQD represented by the formula(4) as the quinacridone derivative and SubPcCl represented by theformula (2-3) as the subphthalocyanine derivative were used. The organicphotoelectric conversion layer in each of the samples was formed byappropriately adjusting a ratio of the quinacridone derivative and thesubphthalocyanine derivative within a range from 90%:10% to 25%:75% involume ratio. Table 4 summarizes materials configuring the organicphotoelectric conversion layer and volume ratios of the materials, typesof quinacridone derivatives used for the organic photoelectricconversion layers, and evaluation results of EQE and responsivity in thesamples 4-1 to 4-9. It is to be noted that each of the evaluationresults of EQE and responsivity is a relative value with reference tothe result in the sample 4-1 as a reference value.

TABLE 4 Constituent Material of Photoelectric Conversion Layer Type ofQD Volume Ratio derivative EQE Responsivity Sample 4-1 Formula (1-1)Formula (2-3) HR 1.0 1.0 50% 50% Sample 4-2 Formula (1-1) Formula (2-3)HR 0.8 0.9 25% 75% Sample 4-3 Formula (1-1) Formula (2-3) HR 1.2 1.3 75%25% Sample 4-4 Formula (1-1) Formula (2-3) HR 0.2 10 10% 90% Sample 4-5Formula (1-1) Formula (2-3) HR 0.1 50 90% 10% Sample 4-6 Formula (3-1)Formula (2-3) HH 2.4 10 50% 50% Sample 4-7 Formula (3-1) Formula (2-3)HH 1.5 90 25% 75% Sample 4-8 Formula (3-1) Formula (2-3) HH 2.6 18 75%25% Sample 4-9 Formula (4-1) Formula (2-3) RR 0.2 4.0 50% 50%

As can be seen from Table 4, in a case where the organic photoelectricconversion layer was formed using the HR-type quinacridone derivativeand the subphthalocyanine derivative, a ratio of the quinacridonederivative and the subphthalocyanine derivative was within a range from25%:75% to 75%:25% in volume ratio, which stably made high EQE andsuperior responsivity compatible. In other words, it was found thatadjusting a volume ratio of the HR-type quinacridone derivative includedin the organic photoelectric conversion layer within a range from 25% to75% both inclusive made it possible to achieve high EQE and superiorresponsivity.

In contrast, in a case where the volume ratio of the HR-typequinacridone derivative was less than 25%, EQE and responsivity werelargely deteriorated. It is considered that an area of an interfacebetween the HR-type quinacridone derivative as the organic p-typesemiconductor and the subphthalocyanine derivative as the organic n-typesemiconductor was reduced, which reduced a possibility that an excitonreached the interface to result in a deterioration in external quantumefficiency. Regarding a deterioration in responsivity, it is consideredthat in a carrier transport process after excitation dissociation, holeswere transported through between the HR-type quinacridone derivatives asthe organic p-type semiconductor; therefore, a possibility that theHR-type quinacridone derivatives were adjacent to each other wasreduced, and holes were not thereby transported efficiently to increasethe falling time, that is, to deteriorate responsivity. Moreover, in acase where the volume ratio of the HR-type quinacridone derivativeexceeded 75%, EQE and responsivity were largely deteriorated. It isconsidered that, as with the case where the volume ratio of the HR-typequinacridone derivative was less than 25%, the area of the interfacebetween the HR-type quinacridone derivative as the organic p-typesemiconductor and the subphthalocyanine derivative as the organic n-typesemiconductor was reduced, which reduced a possibility that an excitonreached the interface to result in a deterioration in external quantumefficiency. Regarding a deterioration in responsivity, it is consideredthat in the carrier transport process after exciton dissociation,electrons were transported through between the subphthalocyaninederivatives as the organic n-type semiconductor; therefore, apossibility that the subphthalocyanine derivatives were adjacent to eachother was reduced, and electrons were not thereby transportedefficiently to increase the falling time, that is, to deteriorateresponsivity.

(Experiment 5)

Next, photoelectric conversion elements (samples 5-1 to 5-14) werefabricated by a method similar to that in the foregoing experiment 1except for the configuration of the organic photoelectric conversionlayer, and external quantum efficiency and responsivity of these sampleswere evaluated. In the present experiment, two kinds of quinacridonederivatives and a subphthalocyanine derivative configured the organicphotoelectric conversion layer, a volume ratio thereof was verified.

As a first type of quinacridone derivative used in the respectivesamples, BMQD represented by the formula (1-7) was used in the samples5-1 to 5-8, DMQD represented by the formula (4-1) was used in thesamples 5-9 and 5-10, DPQD represented by the formula (4-2) was used inthe sample 5-11, BQD represented by the formula (3-4) was used in thesample 5-12, PR122 represented by the formula (3-2) was used in thesample 5-13, and EQD represented by the formula (3-3) was used in thesample 5-14. As a second type of quinacridone derivative, BQDrepresented by the formula (3-4) was used, and as the subphthalocyaninederivative, F₆SubPcCl represented by the formula (2-1) was used in thesamples 3-5. It is to be noted that in each of the samples 5-8, 5-9, and5-12, the second type of quinacridone derivative was not used to formthe organic photoelectric conversion layer. Table 5 summarizes materialsconfiguring the organic photoelectric conversion layer and volume ratiosof the materials, types of quinacridone derivatives used for the organicphotoelectric conversion layers, and evaluation results of EQE andresponsivity in the sample 5-1 to 5-14. It is to be noted that each ofthe evaluation results of EQE and responsivity is a relative value withreference to the result in the sample 5-1 as a reference value.

TABLE 5 Type Configuration of Photoelectric Conversion Layer of QDVolume Ratio derivative EQE Responsivity Sample 5-1 Formula (1-7)Formula (3-4) Formula (2-1) HR + HH 1.0 1.0 25% 25% 50% Sample 5-2Formula (1-7) Formula (3-4) Formula (2-1) HR + HH 0.9 0.9 12.5%  12.5% 75% Sample 5-3 Formula (1-7) Formula (3-4) Formula (2-1) HR + HH 1.2 1.637.5%  37.5%  25% Sample 5-4 Formula (1-7) Formula (3-4) Formula (2-1)HR + HH 0.8 1.5 50% 25% 25% Sample 5-5 Formula (1-7) Formula (3-4)Formula (2-1) HR + HH 1.0 1.7 25% 50% 25% Sample 5-6 Formula (1-7)Formula (3-4) Formula (2-1) HR + HH 0.6 9.0  5% 45% 50% Sample 5-7Formula (1-7) Formula (3-4) Formula (2-1) HR + HH 0.4 2.5 45%  5% 50%Sample 5-8 Formula (1-7) — Formula (2-1) HR 0.4 2.5 50% 50% Sample 5-9Formula (4-1) — Formula (2-1) RR 0.4 5.0 50% 50% Sample 5-10 Formula(4-1) Formula (3-4) Formula (2-1) RR + HH 0.5 7.0 1 1 1 Sample 5-11Formula (4-2) Formula (3-4) Formula (2-1) RR + HH 0.1 30 1 1 1 Sample5-12 Formula (3-4) — Formula (2-1) HH 0.7 10 50% 50% Sample 5-13 Formula(3-2) Formula (3-4) Formula (2-1) HH + HH 0.7 17 1 1 1 Sample 5-14Formula (3-1) Formula (3-4) Formula (2-1) HH + HH 0.8 11 1 1 1

As can be seen from Table 5, it was found that in a case where theorganic photoelectric conversion layer was formed using two kinds, thatis, the HR-type and HH-type quinacridone derivatives, and thesubphthalocyanine derivative, forming the organic photoelectricconversion layer by adjusting a volume ratio of the two kinds ofquinacridone derivatives within a range from 33% to 67% both inclusivemade high EQE and superior responsivity compatible. It is to be notedthat in a case where the volume ratio of the two kinds, that is, HR-typeand HH-type quinacridone derivatives was within a range from 25% to 75%both inclusive, but the content of the HR-type quinacridone derivativewas extremely small as with the sample 5-6, a further improvement inresponsivity was not observed, and responsivity was substantially equalto that in a case where only one kind, that is, the HH-type quinacridonederivative was used. Moreover, in a case where the content of theHH-type qunacridone derivative was extremely small as with the sample5-7, a further improvement in EQE was not observed, and EQE wassubstantially equal to that in a case where only one kind, that is, theHR-type quinacridone derivative was used. Accordingly, it was found thatin a case where the organic photoelectric conversion layer was formedusing two kinds, that is, the HR-type and HH-type quinacridonederivatives, the ratio of the HR-type quinacridone derivative waspreferably adjusted within a range from 33% to 67% both inclusive involume ratio.

Although the description has been given by referring to the first andsecond embodiments and the examples, the contents of the presentdisclosure are not limited to the foregoing embodiments, etc., and maybe modified in a variety of ways. For example, the foregoing embodimentshave exemplified, as the photoelectric conversion element (thesolid-state imagine device), a configuration in which the organicphotoelectric converter 11G detecting green light and the inorganicphotoelectric converters 11B and 11R respectively detecting blue lightand red light are stacked; however, the contents of the presentdisclosure is not limited thereto. In other words, the organicphotoelectric converter may detect red light or blue light, and theinorganic photoelectric converter may detect green light.

Moreover, the number of organic photoelectric converters, the number ofinorganic photoelectric converters, a ratio between the organicphotoelectric converters and the inorganic photoelectric converters arenot limited, and two or more organic photoelectric converters may beprovided, or color signals of a plurality of colors may be obtained byonly the organic photoelectric converter. Further, the contents of thepresent disclosure is not limited to a configuration in which organicphotoelectric converters and inorganic photoelectric converters arestacked along the vertical direction, and organic photoelectricconverters and inorganic photoelectric converters may be disposed sideby side along a substrate surface.

Furthermore, the foregoing first and second embodiments have exemplifiedthe configuration of the back-side illumination type solid-state imagingdevice; however, the contents of the present disclosure are applicableto a front-side illumination type solid-state imaging device. Further,it may not be necessary for the solid-state imaging device (thephotoelectric conversion element) of the present disclosure to includeall components described in the foregoing embodiments, and thesolid-state imaging device of the present disclosure may include anyother layer.

It is to be noted that the effects described in the presentspecification are illustrative and non-limiting, and other effects maybe included.

It is to be noted that the present disclosure may have the followingconfigurations.

[1]

A photoelectric conversion element, including:

a first electrode and a second electrode facing each other; and

a photoelectric conversion layer provided between the first electrodeand the second electrode, and including a first quinacridone derivativerepresented by the following formula (1),

(where each of R1 and R2 is independently one of an alkyl group, analkenyl group, an alkynyl group, an aryl group, a cyano group, a nitrogroup, and a silyl group, each of m1 and m2 is independently 0 or aninteger of 1 or more, in a case where each of m1 and m2 is 2 or more,two or more R1 are optionally bound to one another to form a ring andtwo or more R2 are optionally bound to one another to form a ring, andR3 is one of an alkyl group, an aryl group, and a heterocyclic group.)

[2]

The photoelectric conversion element according to [1], in which thephotoelectric conversion layer further includes a subphthalocyaninederivative represented by the following formula (2),

(where each of R4 to R15 is independently a hydrogen atom, a halogenatom, a straight-chain, branched, or cyclic alkyl group, a thioalkylgroup, a thioaryl group, an arylsulfonyl group, an alkylsulfonyl group,an amino group, an alkylamino group, an arylamino group, a hydroxygroup, an alkoxy group, an acylamino group, an acyloxy group, a phenylgroup, a carboxy group, a carboxyamide group, a carboalkoxy group, anacyl group, a sulfonyl group, a cyano group, and a nitro group, anyadjacent ones of R4 to R15 are optionally bound to one another to form aring, and X is an anionic group.)

[³]

The photoelectric conversion element according to [1] or [2], in which acontent of the first quinacridone derivative included in thephotoelectric conversion layer is within a range from 25% to 75% bothinclusive in volume ratio.

[4]

The photoelectric conversion element according to [2] or [3], in whichthe photoelectric conversion layer includes a second quinacridonederivative represented by the following formula (3) in addition to thefirst quinacridone derivative and the subphthalocyanine derivative,

(where each of R16 and R17 is independently one of an alkyl group, analkenyl group, an alkynyl group, an aryl group, a cyano group, a nitrogroup, and a silyl group, each of n1 and n2 is independently 0 or aninteger of 1 or more, and in a case where each of n1 and n2 is 2 ormore, two or more R16 are optionally bound to one another to form a ringand two or more R17 are optionally bound to one another to form a ring.)

[⁵]

The photoelectric conversion element according to [4], in which a totalcontent of the first quinacridone derivative and the second quinacridonederivative included in the photoelectric conversion layer is within arange from 25% to 75% both inclusive in volume ratio.

[6]

The photoelectric conversion element according to [4] or [5], in which acontent of the first quinacridone derivative in the photoelectricconversion layer including the first quinacridone derivative and thesecond quinacridone derivative is within a range from 33% to 67% bothinclusive in volume ratio.

[⁷]

A solid-state imaging device provided with pixels each including one ora plurality of organic photoelectric converters, each of the organicphotoelectric converters including:

a first electrode and a second electrode facing each other; and

a photoelectric conversion layer provided between the first electrodeand the second electrode, and including a first quinacridone derivativerepresented by the following formula (1),

(where each of R1 and R2 is independently one of an alkyl group, analkenyl group, an alkynyl group, an aryl group, a cyano group, a nitrogroup, and a silyl group, each of m1 and m2 is independently 0 or aninteger of 1 or more, in a case where each of m1 and m2 is 2 or more,two or more R1 are optionally bound to one another to form a ring andtwo or more R2 are optionally bound to one another to form a ring, andR3 is one of an alkyl group, an aryl group, and a heterocyclic group.)

[8]

The solid-state imaging device according to [7], in which the one orplurality of organic photoelectric converters, and one or a plurality ofinorganic photoelectric converters that performs photoelectricconversion in a wavelength region different from a wavelength region ofthe organic photoelectric converters are stacked in each of the pixels.

[9]

The solid-state imaging device according to [8], in which

the inorganic photoelectric converter is formed to be embedded in asemiconductor substrate, and

the organic photoelectric converter is formed on a first surface side ofthe semiconductor substrate.

[10]

The solid-state imaging device according to any one of [7] to [9], inwhich

the organic photoelectric converter performs photoelectric conversion ongreen light, and

an inorganic photoelectric converter that performs photoelectricconversion on blue light and an inorganic photoelectric converter thatperforms photoelectric conversion on red light are stacked in thesemiconductor substrate.

This application claims the benefit of Japanese Priority PatentApplication JP2015-215966 filed on Nov. 2, 2015, the entire contents ofwhich are incorporated herein by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A photoelectric conversion element, comprising: a first electrode anda second electrode facing each other; and a photoelectric conversionlayer provided between the first electrode and the second electrode, andincluding a first quinacridone derivative represented by the followingformula (1),

(where each of R1 and R2 is independently one of an alkyl group, analkenyl group, an alkynyl group, an aryl group, a cyano group, a nitrogroup, and a silyl group, each of m1 and m2 is independently 0 or aninteger of 1 or more, in a case where each of m1 and m2 is 2 or more,two or more R1 are optionally bound to one another to form a ring andtwo or more R2 are optionally bound to one another to form a ring, andR3 is one of an alkyl group, an aryl group, and a heterocyclic group.)2. The photoelectric conversion element according to claim 1, whereinthe photoelectric conversion layer further includes a subphthalocyaninederivative represented by the following formula (2),

(where each of R4 to R15 is independently a hydrogen atom, a halogenatom, a straight-chain, branched, or cyclic alkyl group, a thioalkylgroup, a thioaryl group, an arylsulfonyl group, an alkylsulfonyl group,an amino group, an alkylamino group, an arylamino group, a hydroxygroup, an alkoxy group, an acylamino group, an acyloxy group, a phenylgroup, a carboxy group, a carboxyamide group, a carboalkoxy group, anacyl group, a sulfonyl group, a cyano group, and a nitro group, anyadjacent ones of R4 to R15 are optionally bound to one another to form aring, and X is an anionic group.)
 3. The photoelectric conversionelement according to claim 1, wherein a content of the firstquinacridone derivative included in the photoelectric conversion layeris within a range from 25% to 75% both inclusive in volume ratio.
 4. Thephotoelectric conversion element according to claim 2, wherein thephotoelectric conversion layer includes a second quinacridone derivativerepresented by the following formula (3) in addition to the firstquinacridone derivative and the subphthalocyanine derivative,

(where each of R16 and R17 is independently one of an alkyl group, analkenyl group, an alkynyl group, an aryl group, a cyano group, a nitrogroup, and a silyl group, each of n1 and n2 is independently 0 or aninteger of 1 or more, and in a case where each of n1 and n2 is 2 ormore, two or more R16 are optionally bound to one another to form a ringand two or more R17 are optionally bound to one another to form a ring.)5. The photoelectric conversion element according to claim 4, wherein atotal content of the first quinacridone derivative and the secondquinacridone derivative included in the photoelectric conversion layeris within a range from 25% to 75% both inclusive in volume ratio.
 6. Thephotoelectric conversion element according to claim 4, wherein a contentof the first quinacridone derivative in the photoelectric conversionlayer including the first quinacridone derivative and the secondquinacridone derivative is within a range from 33% to 67% both inclusivein volume ratio.
 7. A solid-state imaging device provided with pixelseach including one or a plurality of organic photoelectric converters,each of the organic photoelectric converters comprising: a firstelectrode and a second electrode facing each other; and a photoelectricconversion layer provided between the first electrode and the secondelectrode, and including a first quinacridone derivative represented bythe following formula (1),

(where each of R1 and R2 is independently one of an alkyl group, analkenyl group, an alkynyl group, an aryl group, a cyano group, a nitrogroup, and a silyl group, each of m1 and m2 is independently 0 or aninteger of 1 or more, in a case where each of m1 and m2 is 2 or more,two or more R1 are optionally bound to one another to form a ring andtwo or more R2 are optionally bound to one another to form a ring, andR3 is one of an alkyl group, an aryl group, and a heterocyclic group.)8. The solid-state imaging device according to claim 7, wherein the oneor plurality of organic photoelectric converters, and one or a pluralityof inorganic photoelectric converters that performs photoelectricconversion in a wavelength region different from a wavelength region ofthe organic photoelectric converters are stacked in each of the pixels.9. The solid-state imaging device according to claim 8, wherein theinorganic photoelectric converter is formed to be embedded in asemiconductor substrate, and the organic photoelectric converter isformed on a first surface side of the semiconductor substrate.
 10. Thesolid-state imaging device according to 9, wherein the organicphotoelectric converter performs photoelectric conversion on greenlight, and an inorganic photoelectric converter that performsphotoelectric conversion on blue light and an inorganic photoelectricconverter that performs photoelectric conversion on red light arestacked in the semiconductor substrate.